#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef double db;

#define in read()
#define pii pair<int,int>
#define fi first
#define se second
#define FILE(x) freopen(x".in","r",stdin);\
	freopen(x".out","w",stdout);
#define pb push_back

int read(){
	int x = 0,sgn = 1;char ch = getchar();
	for(;!isdigit(ch);ch = getchar()) if(ch == '-') sgn = -1;
	for(;isdigit(ch);ch = getchar()) x = (x<<1)+(x<<3)+(ch^48);
	return x*sgn;
}

const int N = 1010;
const int inf = 0x3f3f3f3f;

ll dis[N],cost;
int incf[N],h[N],fro[N],cnt = 1,n,m,S,T,s[N];
bool vis[N];
struct edge{int v,w,c,nxt;}e[N<<5];
void link(int x,int y,int w,int c){e[++cnt] = (edge){y,w,c,h[x]};h[x] = cnt;e[++cnt] = (edge){x,0,-c,h[y]};h[y] = cnt;}

bool spfa(){
	memset(dis,0x3f,sizeof(dis)); memset(vis,0,sizeof(vis)); dis[S] = 0; vis[S] = 1; queue<int> q; q.push(S); incf[S] = inf;
	while(q.size()){
		int x = q.front(); q.pop();
		for(int i = h[x],y;i;i = e[i].nxt){
			if(dis[y = e[i].v] > dis[x] + e[i].c && e[i].w){
				dis[y] = dis[x] + e[i].c; incf[y] = min(incf[x],e[i].w); fro[y] = i; if(!vis[y]) vis[y] = 1,q.push(y);
			}
		}vis[x] = 0;
	}return dis[T] < 0x3f3f3f3f3f3f3f3f;
}

void update(){
	int x = T; cost += dis[T] * incf[T];
	while(x ^ S){
		int i = fro[x]; e[i].w -= incf[T]; e[i ^ 1].w += incf[T]; x = e[i ^ 1].v;
	}
}

int main (){
#ifndef ONLINE_JUDGE
	freopen("1.in","r",stdin);
#endif
	n = in,m = in; S = 0,T = n + 2; link(S,1,inf,0);
	for(int i = 1;i <= n;i++) link(i,i+1,inf-in,0);
	link(n + 1,T,inf,0);
	for(int i = 1;i <= m;i++){
		int u = in,v = in,w = in;
		link(u,v+1,inf,w);
	}
	while(spfa()) update(); printf("%lld\n",cost);
	return 0;
}

